Thomas' label, Esoteric Recordings/Cherry Red Records, confirmed on Facebook that Thomas died suddenly at his home in Surrey, England. No cause of death was announced, but Thomas disclosed in 2014 that he had been diagnosed with prostate cancer, Billboard reported.

In a statement four years ago, Thomas said “My cancer was inoperable but I have a fantastic doctor who immediately started me on a new treatment that has had 90% success rate,” The Daily Mail reported.

"We are deeply shocked by his passing and will miss his warmth, humor and kindness," the label wrote. "It was a privilege to have known and worked with him and our thoughts are with his family and his wife Lee at this sad time."

Thomas's flute solo was a key ingredient on one of the band’s biggest hits, “Nights in White Satin,” and he sang lead vocals on several songs, including “Legend of a Mind,” a tribute to LSD guru Timothy Leary.

The band is scheduled to be inducted into the Rock and Roll Hall of Fame in Cleveland in April, Billboard reported.

Moody Blues bassist John Lodge tweeted Sunday that, "Ray and I have been on this magical journey through life together since we were 14. ... two young kids from Birmingham who reached for the stars...and we made it together. El Riot you will always be by my side." Thomas and Lodge played together in their band El Riot and the Rebels in the early Sixties, Rolling Stone reported.

In 1964, Thomas and keyboardist Michael Pinder formed the Moody Blues with drummer Graeme Edge, bassist Clint Warwick and guitarist Denny Laine. That lineup would release the hit “Go Now” and the 1965 LP “The Magnificent Moodies,” which featured Thomas on lead vocals for "It Ain't Necessarily So."

It is with profound sorrow and sadness that Cherry Red Records and Esoteric Recordings regret to announce that Ray...

The Moody Blues replaced Laine with Justin Hayward and Warwick with Lodge to form the band's classic lineup. Thomas played on all of the Moody Blues’ albums until his retirement in 2002.

Ray and I have been on this magical journey through life together since we were 14...two young kids from Birmingham who reached for the stars...and we made it together. El Riot you will always be by my side #moodyblues@rockhall#Moodiescruise